1. Technical Field
The present invention relates generally to methods useful in constructing a reciprocator. In particular, the invention relates to a method of constructing a reciprocator and moving element, and a method of producing a non-contacting alignment of elements.
2. Related Art
Many reciprocating machines that use linear motors require unlubricated elements to operate in very close clearance and free-running relation. Examples of these type machines include: free-piston Stirling engines, thermoacoustic engine-generators, various free-piston cryocoolers, gas-cycle refrigeration machines, and gas compressors driven by linear motors. In these linear motor or reciprocator driven machines, a moving element such as a piston must be mated to a cylinder bore in which it reciprocates, guided by some bearing or flexing suspension system. U.S. Pat. No. 5,522,214 to Beckett et al. discloses an exemplary spiral suspension. In order for the moving element of the reciprocator to run freely in the respective cylinder bore while maintaining an effective pressure barrier, very close clearances are required. In particular, coaxiality of the piston with both the cylinder and linear motor mating surface is essential. Typically, the machining required to provide these close fits must be very precise because the parts, e.g., motor stator, suspension, piston and cylinder, are tooled individually and must be stacked together or mated once completed. Where numerous close clearance free-running parts are necessary, the precision required to create the parts becomes very time consuming and expensive.
In view of the foregoing, there is a need in the art for an inexpensive and reliable way to produce close-fitting but non-contacting fits between elements, such as flexure-supported moving elements and cylinder assemblies, as used in reciprocating machine powered tools.
The present invention provides a method of producing a moving element for a reciprocating machine that assures co-axiality of the moving element and reciprocator, and perpendicularity of a pilot face of the reciprocator with respect to the moving element and a motion axis thereof.
In a first aspect of the invention is provided a method of constructing a reciprocator and a moving element of the reciprocator, the reciprocator having a reciprocation axis along which the moving element moves, the method comprising the steps of: connecting the moving element to the reciprocator via a suspension that allows reciprocation and substantially restricts non-axial motion of the moving element relative to the reciprocator; simultaneously rotating the moving element and the reciprocator substantially about the reciprocation axis; and machining a diameter of the moving element and a diameter of the reciprocator.
A second aspect provides a method of producing a non-contacting alignment between a first element, coupled to a reciprocator for reciprocating movement along a reciprocation axis, and a second element, the method comprising the steps of: connecting the first element to the reciprocator via a suspension that allows reciprocation and substantially restricts non-axial motion of the first element relative to the reciprocator; simultaneously rotating the first element and the reciprocator about the reciprocation axis; machining the first element to a first outer diameter and the reciprocator to a second outer diameter; and machining the second element to have a first inner diameter for mating to the first outer diameter, a second inner diameter for mating to the second outer diameter and a face.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.